


Fertile Ground

by Anonymous



Category: Marvel, Marvel Cinematic Universe
Genre: Body Modification, Happy Ending, M/M, Mildly Dubious Consent, Oviposition, cap-im kink meme fill, due to circumstances, due to the serum, some body horror
Language: English
Status: Completed
Published: 2017-07-23
Updated: 2017-07-23
Packaged: 2018-12-05 17:03:00
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 2,880
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/11582397
Author URL: https://archiveofourown.org/
Summary: Fill for Cap-Ironman Kink Meme prompt:One of those stories where Project Rebirth makes Steve not quite human. The changes aren't immediately obvious and were generally kept quiet, but they lead to some interesting sexual urges down the line.orSteve lovingly fills Tony with his eggs.





	Fertile Ground

The first time it had happened, Steve had written it off as a hallucination or fever dream.

He had finally gotten ten minutes alone, rare in a military camp packed with people. The first two minutes he took to simply breathe and enjoy the lack of eyes watching him. Then, his hands slipped down to unbutton his pants. It had been awhile because while the etiquette was simply to avert your eyes and pretend you didn’t see, people couldn’t seem to stop staring at Steve - at Captain America.

Steve’s cock rapidly rises to the occasion as he pulls up a generic fantasy. He wraps his hand tight around himself and he pulls with quick, punishing strokes as he imagines something else - sinking into a hot, tight hole that would clutch at his cock, urge him deeper. Legs would wrap around his hips, a voice would beg for him, for Steve, and Steve would kiss them quiet as he gave them everything they wanted and more. His cock, fattened by the serum, would slide in and out and oh - would he go slow? He waivers between imagining slow, deep thrusts and fucking hard and fast but his hand speeds up, the tell-tale heat already coiling.

Then something shifts, like a muscle pulling tight, one he didn’t even know he had. He opens his eyes and looks down and - and if this was real, Steve would be horrified but it’s not, it can’t be - the slit of his cock is gaping open with a thick, white fluid that dribbles out with every stroke. The hand, _his_ hand, keeps stroking, and Steve can feel the pressure in his hips, in his cock. Something, something much bigger, much harder is coming out and Steve watches, frozen except for his hand continuing to move, as that pressure builds and builds and -

An off-white spherical _thing_ is squeezed out of the gaping hole in his cock and falls to the ground with a splat. The pressure from his cock is released, but not from his hips and Steve can feel another shift, another something that’s going to come.

His hand flies off his cock, jerks away like he should’ve had the brain function to do so ages ago. Except this isn’t real, right? This isn’t actually happening, this isn’t his body. With shaking hands, Steve tucks himself back into his pants while wiping away the thick, white fluid that is still draining out. He’s still hard, his pulse still races, but he kicks dirt over the thing - the thing that did _not_ just come out of his body - with calm dissociation.

Steve staggers back to his bunk and tells himself it was a hallucination. A fever dream. They say he can’t get sick because of the serum, but what do they really know about it, with Erksine dead? Did they know _this_? Because this had never happened before, not before the serum.

Later, much later, Steve will cautiously take his cock out again and it will look normal. Hallucination, he tells himself. His next orgasm is fine. It’s normal. Steve breathes a sigh of relief, and isn’t so hesitant about stroking himself off. Things are fine for the next, the next, the next, the next time until Steve forgets he even had such a weird dream.

 

 

Then Steve falls into bed with Tony Stark. Well, he falls into a relationship with Tony first and then falls into his bed. Steve even literally falls, too, by way of tripping over his pants because he’s too busy staring at Tony’s naked form to pay attention to what his own body is doing.

Steve learns a lot. He learns that Tony’s hand wrapped around Steve’s cock is much, much hotter than his own. He learns places to touch Tony that make him desperate with need. He learns that Tony knows exactly how to use his mouth, whether it be by whispering words into Steve’s ear or by licking his way down Steve’s body.

He learns when not to push and let Tony have his space - or at least he’s getting better at it. He learns that cheeseburgers will always grant him access to the workshop. He learns that Tony is too generous, too giving, and he learns what it’s like to have his heart stop when Iron Man falls out of the sky. Steve learns a lot.

Steve also learns that he wasn’t hallucinating, that time before the ice.

“Come on, come on, I’m ready,” Tony whines as he rocks his hips back onto Steve’s fingers. Steve had him splayed out on his back, tan skin glistening against the white sheets, as he tortured Tony with too much prep - or so Tony would say.

“No you’re not,” Steve replies with a laugh, but he does add a third finger into those slipping in and out of Tony’s ass, stretching him just a bit more. “Always so impatient.”

“I want you,” Tony pleads. Steve’s gaze fixes on Tony’s hole, clenching and relaxing around Steve’s fingers as slips them inside. His cock throbs as he thinks about that tight, clenching heat around him instead. Steve barely has enough patience to compensate for Tony’s lack, and he clings to it now.

“Steve, please!”

Steve leans forward and kisses Tony quiet. Tony’s rigid and leaking cock is pressed between their stomachs, and Tony moans into Steve’s mouth. Pressing Tony into the mattress, so close to sinking into him - Steve’s patience wears too thin. He slides his fingers out and slicks up his cock with a few quick strokes. Then Steve presses in, slow but firm, and catches Tony’s gasps directly from his mouth.

He hadn’t stretched Tony enough, not enough to make it easy. Steve pushes his way in with short, gentle strokes and tries not to focus too much on how tight, how hot Tony is around him. He groans into Tony’s mouth as he finally bottoms out and Tony squeezes around his entire length for a solid moment.

“I love your dick,” Tony comments, gasping for breath. “Come on, babe. Fuck me. _Please_.”

Steve would like to think that positive reinforcement is a good thing, and so he slides back, almost all the way, and then in with a slow, solid thrust. He also has to admit that he’s terrible at not giving into Tony when he asks like that.

He lets himself get lost in a slow, sure rhythm. He knows it isn’t entirely what Tony wants, with Tony’s hips trying to urge Steve faster, deeper, harder, but it’s been too long and Steve wants to fuck Tony just like this for hours. Or at least until he gives into Tony again.

Tony wraps his legs around Steve’s hips, squeezing. “Mmm, you feel so good,” Tony breathes into Steve’s ear. “Yes... _Steve_. Harder?”

Steve complies, can do nothing else. He snaps his hips, fucking into Tony faster and harder until Tony is keening. Steve is so focused on watching Tony that he almost doesn’t notice when there’s a pressure in his cock, rather than just on it. It’s new - not a building orgasm, Steve realizes. He doesn’t know what it is.

“What? What’s wrong?” Tony asks, panting, as Steve freezes.

“I...I don’t...” Steve stutters. He avoids Tony’s eyes, his face hot, as he pulls out and off. He’s going to feel like an idiot if it’s nothing, but as soon as he sees his cock and the gaping hole, Steve knows.

He scrambles away from Tony and the hand reaching out for him.

“Steve?”

“I don’t...I don’t,” is all Steve can gasp. He feels an intense pressure inside his cock. It’s not pain, not really, but it swells to such a point that it’s all he can focus on.

“Steve, what...” Tony trails off as he slides closer. He doesn’t need Steve to point out the problem, though. Tony’s hand is already reaching slowly for Steve’s cock. “Holy fuck. Does that hurt? Can I touch you?”

Steve nods, his entire body shaking, and Tony’s fingers gently caress the rim of the hole that makes up the tip of Steve’s cock. Steve bites his lip through the full body shudder that overtakes him.

“That hurt?” Tony asks, his hand hovering.

“N-no,” is all Steve can manage. His entire body feels wired, like electricity is coursing through his veins, but the pressure inside his cock is getting to unbearable levels.

“Oh my God. Steve this is... this is not normal. Do you have an alien STD? I have to call medical,” Tony rambles. Steve grabs him before Tony rolls away to get his phone.

“Don’t,” Steve forces out. The last thing he’ll be able to stand is SHIELD testing him, testing _this_. “It’s - it’s from the serum.”

“The serum?” Tony repeats, eyes wide.

“I - this has happened before,” Steve admits through gritted teeth. The pressure, the _thing,_ inside him is too much. He grips his cock and strips it, fast and harsh. “I don’t know, I don’t know what it is. But something - the serum did something and now a, a thing needs to come out. I don’t know,” Steve pleads, meeting Tony’s gaze. Fear chokes him, because he realizes that this, whatever this is, could cost him Tony.

“A thing?” Tony repeats, voice rising. “A thing needs to come out? Of your dick? What, like a gnome? Flowers? What _thing_?”

“I don’t know!” Steve shouts and he wrings his cock because the pressure is driving him crazy.

“Stop that!” Tony snaps and slaps Steve’s hand away from his cock. “You’re hurting yourself.”

“I need -” Steve starts, but then the rest is punched out in a sigh of relief as Tony’s hand, firm but gentle, closes around his cock and strokes. The pressure doesn’t lessen, but it shifts. It shifts closer to the tip of his cock, and at least a little bit of fear is chipped away because it should all be fine as soon as this thing is out.

“Steve. Talk,” Tony orders, but his hand doesn’t stop stroking.

Steve gives himself a moment to breathe as the pressure shifts again, just a little. Then he spills the entire account from what he can remember, what he thought was simply a hallucination. A fever dream. Something not real.

“Sounds like a kidney stone. But for your dick,” Tony comments when Steve is finished. “Is it painful?”

“Not really,” Steve says. “There’s just... pressure. It gets intense.”

“This is helping?” Tony clarifies, his hand still stroking. He’d switched hands, and Steve flushes as Tony peers down into the hole of Steve’s cock.

“Yes...”

Tony raises an eyebrow at him.

“It is!” Steve defends. “It’s still just... intense. Last time it didn’t take this long.” And wow, Steve does not want to have to go to medical about this issue. What if surgery is the only option? He shivers.

“Hmm...” is all Tony says.

Steve tries to relax, because maybe that would help speed this up. The thing, whatever it is, has definitely shifted but still has a long way to go before it’s close to exiting Steve’s body.

Tony straddles him, and in a single, fluid move sinks onto Steve’s cock. Steve yelps, body curling up toward Tony, but _hot, tight, yesyesyes_ , is all Steve can think as he grabs Tony’s hips and holds on.

“Tony,” Steve breathes through gritted teeth, trying to protest, but can do nothing to actually stop Tony from sinking all the way down. Tony clenches, and Steve moans, falling back onto the bed.

“Sex started this, so that’s how we’ll finish it,” Tony gasps as he sits, readjusting to Steve’s cock inside him, clenching and relaxing and clenching again.

“ _Tony_ ,” Steve says, but his hips grind up. The pressure inside his cock is still there, but every miniscule thrust up shifts it. Steve can feel it moving as he rocks into Tony, and it’s such a relief that Steve feels high. “Tony!”

“Just like that, baby, yeah,” Tony praises as he rocks his hips with Steve. “I got you.”

“Tony,” Steve gasps again. He’s close, so close, and then suddenly he feels it squeezing out of him and it’s gone. It’s in Tony.

“ _Oh_ ,” Tony gasps, hips stuttering.

“Tony?” Steve asks, fear rising not only for the expression on Tony’s face but also because he feels a new pressure, one that shifts from his stomach to his cock.

“It’s... oh,” Tony replies, his face twisted in confusion. “Is that it?”

Steve closes his eyes. “There’s another one,” he whispers. He can’t stop his hips from grinding up into Tony, but he says anyway, “You don’t have to - Tony, please don’t -”

“We might need to switch positions,” Tony interrupts, his hips circling and making Steve lose his mind. “It’s... it would be better if I was on my back again.”

“Are you sure?” Steve asks, but he’s rolling them anyway. He can’t bear to take himself out of Tony, not unless Tony asks him to, and so brings Tony down, chest to chest, before turning them over.

“Yeah, I think...” Tony says, eyes wide and tongue darting out to lick his lips. “Just... just keeping going, yeah? Until we’re all done.”

Steve buries his face in Tony’s neck, kissing him, clutching Tony to him because he doesn’t deserve this. He will pay whatever Tony wants later in repayment for this.

Steve keeps his thrusts short, and it works to shift whatever Steve has in his body into Tony. He does his best not to jostle Tony too much, whose faces tenses and slackens as Steve deposits more and more into Tony’s body.

It’s...God, it’s good. Steve feels guilty enjoying it, but there’s a bright burst of pleasure now each time Steve is relieved of the pressure, each time Steve pushes this into Tony. He wraps Tony in his arms, kisses every piece of skin within reach in apology, and holds back his groans.

“Steve. It’s... I’m so full,” Tony whispers to him. Steve is not so far gone that he can’t hear the amazement in his tone.

“Tony?”

Tony hums, eyes screwed shut. He shifts his hips up, clenches down, and moans in combination with Steve at the feeling. “Yeah, just... you have more, right?”

“God, Tony,” Steve moans into Tony’s skin, his voice breaking. “You’re... you’re _amazing._ ” His hips grind into Tony, and now Steve lets endearments flow from his lips. “You’re doing so well, baby.”

Steve’s hand slides down Tony’s body, intending on feeling any potential bulge in Tony’s abdomen as Steve deposits yet another. He runs into Tony’s cock, hard and leaking, and grips it.

“Steve,” Tony gasps, back arcing.

“I’m almost done,” Steve promises, pulling back to watch Tony’s face. “You can come, baby. You’ve done so well.”

Tony whines, writhes, pleads, and it doesn’t take more than a few strokes for him to come. He tightens painfully around Steve and what Steve has fucked into him, and Steve pants into Tony’s neck as he slams into Tony, forcing his cock in and out.

There’s one, two more after Tony comes and then Steve can feel the emptiness, in a place below his stomach that he didn’t know had been full. Steve gasps for air, almost in shock. His orgasm slams through him, taking him by surprise. He comes and comes and comes, and he can imagine his fluid coating the objects already in Tony’s body, seeping and filling up the cracks.

Tony is completely full of Steve, and Steve grinds further into Tony at the thought.

“All done?” Tony pants as Steve relaxes into him. Steve can feel a hand come up and card his hair. Steve nods into Tony’s chest.

“Tony, I...”

“Don’t. Not now,” Tony sighs. His body melts into the mattress, and Steve slips out of him and shifts to the side so as not to crush him. “Just...later,” he slurs.

“Okay,” Steve agrees. His hand skims down Tony’s body, just checking, and Tony hums, eyes closed. Steve’s hand then hits Tony’s abdomen, and he gulps when he realizes that there is indeed a distinct bulge. He rests his hand on it, not able to curb the sharp, possessive heat that flares through him.

“Very, very full,” Tony mumbles with a sigh. “They’ll have to come out.”

“Later?” Steve prompts, hand frozen where he can feel the unnatural bump.

“Later,” Tony agrees.

Steve kisses the skin, right by his hand, and Tony sighs in contentment. Steve wants to look, wants to see what it looks like in Tony’s gaping hole where lube and Steve’s come is trickling out, but he swallows the urge and curls up next to Tony.

He leaves his hand on his abdomen, though, even if he knows that Tony’s snort of amusement is because of it.

 

 

“Eggs! You lay eggs!” Tony crows in amusement when he finishes the analysis.

“What?!”

“Oh my God, Captain America lays eggs! Like a chicken! Or a frog, or a fish, or - of course! Steve, you’re part platypus!”

“Tony!” Steve protests.

But Steve lets Tony mock him all he wants (in private, because neither want to explain this process to a third party) because whenever that pressure builds in Steve’s abdomen, Tony lets Steve open him up and fill him with his eggs until he’s bursting.


End file.
